1. Field of the Invention
The present invention relates to a caliper for a brake, and, more particularly, a brake caliper having a prefabricated, cast-in-place cylinder liner.
2. Description of the Related Art
Disk brakes are widely known and used in which a caliper straddles the rim of a disk which co-rotates with a wheel or shaft. Friction pads are disposed between the caliper and the disk on either side of the disk. One side of the caliper is provided with a hydraulic cylinder and a piston which causes the disk to be pinched between the pads, thus slowing or stopping rotation of the disk.
As shown in FIG. 1, brake calipers of the prior art have had a cylinder bore B formed by machining directly into the body of the caliper C. With this approach, since the bore is formed after the caliper body is cast, it is necessary to leave an opening 0 in the leg of the disk opposite the bore in order to provide clearance for machining tools. Therefore, the material used for the caliper must be machinable to the extent that a smooth surface is required for the bore B, and strong enough to bear the stresses imposed upon application of the brakes, even though a substantial portion of one leg of the caliper is absent.
To meet the aforementioned machinability and strength criteria, cast or molded brake calipers of the past have been made of iron or steel. These metals are quite heavy, and the weight they add to a vehicle exacts a penalty in fuel efficiency. While lighter metals are known, such as aluminum, such materials are either not adequately machinable, not sufficiently strong, or not economical.
Brake calipers are subject to concentrated bending stresse's in the bridge portion connecting the two legs. To bear these stresses, it has been necessary to thicken the bridge portion, thus adding weight.
Furthermore, the machining of the cylinder bore into a fully formed caliper is made more difficult due the weight and bulkiness of the caliper. Precise locating of the bore may also be more difficult.
Accordingly, there is an unmet need for a brake caliper which is lightweight and economically fabricated, yet which provides adequate strength and a readily machined bore.